The benzofluorenes have been explored in the organic chemical literature to some extent. Lansbury and Fountain showed 11-phenyl-11H-benzo[a]fluorene in J. Am. Chem. Soc. 90, 6544 (1968). Dilthey showed 11-(4-bromophenyl)-11H-benzo[a]fluorene, J. Prakt. Chem. 2, 109, 319 (1925). However, it appears that benzofluorenes have not been extensively explored by pharmaceutical chemists.
For some years, however, compounds with anti-estrogenic and estrogenic activity have been studied. A number of such compounds have been shown to have useful anti-neoplastic activity; see, for example, Jones, U.S. Pat. No. 4,418,068, which shows a series of benzo[b]thiophenes.
More recently, the medical and pharmaceutical arts have been attempting to focus on the problem of bone loss in older patients, particularly post-menopausal women. It has been shown that there is a relationship between estrogen activity and the prevention or even reversal of such bone loss, but the problem is by no means solved at the present time.